The present invention is related to nano-particles comprising a shell and a relatively polar core, their preparation, and their industrial applications. More particularly, the shell of the nano-particle comprises a polymer formed from conjugated diene monomers, while the core comprises a polymer formed from vinyl monomers substituted by at least a polar group.
Electrorheological (ER) fluids, alternatively known as electroviscous fluids, electroresponsive fluids, electrorestrictive fluids or jammy fluids, are colloidal dispersions of polymeric particles in a low conductivity continuous medium. When exposed to an external electric field, ER fluids show pronounced changes in flow properties, i.e., from liquid-like to solid-like, with typical response times in the order of milliseconds. This change is reversible as the liquid-like state returns upon removal of the electric field. This capability of ER fluids allows a variety of mechanical systems to use ER fluids to replace standard electromechanical elements which require a rapid response interface between electronic controls and mechanical devices. The technology greatly expands the number of repetitions a mechanical device can perform. Therefore, a continuous and strong interest in industry is to synthesize novel polymer nano-particles useful in ER fluids.
Polymer nano-particles, on the other hand, have attracted increased attention over the past several years in many other fields including tire, information technology, medicine and healthcare, catalysis, combinatorial chemistry, protein supports, magnets, and photonic crystals etc. Nano-particles can be discrete particles uniformly dispersed throughout a host composition. For example, polystyrene microparticles prepared by anionic dispersion polymerization and emulsion polymerization have been used as a reference standard in the calibration of various instruments, in medical research and in medical diagnostic tests.
However, preparation of some polymer nano-particles, e.g., those with a polarized core, is notoriously difficult. For example, even at −78° C., anionic polymerization of 4-vinyl pyridine goes so fast that some negative impacts emerge, such as poor nano-particle formation and difficulty in monitoring the reaction.
Advantageously, the present invention has developed novel nano-particles comprising a shell and a polar core, which are particularly useful in ER fluids, polymeric product, rubber composition, tire product, hard disk drive gasket, matrix composition, information technology, medicine and healthcare, and engine mount etc.